Enhanced Water Management of Polymer Electrolyte Fuel Cells with Additive-Containing Microporous Layers

Abstract

This work describes the performance improvement of a polymer electrolyte fuel cell with a novel class of microporous layers (MPLs) that incorporates hydrophilic additives: one with 30 μm aluminosilicate fibers and another with multiwalled carbon nanotubes with a domain size of 5 μm.Higher current densities at low potentials were observed for cells with the additive-containing MPLs compared to a baseline cell with a conventional MPL, which correlate with improvements in water management. This is also observed for helium and oxygen experiments and by the lower amount of liquid water in the cell, as determined by neutron radiography. Furthermore, carbon-nanotube-containing MPLs demonstrates improved durability compared to the baseline MPL. Microstructural analyses including nanotomography demonstrate that the filler material in both the additive-containing MPLs provide preferential transport pathways for liquid water, which correlate with ex situ measurements. The main advantage provided by these MPLs is improved liquid-water removal from the cathode catalyst layer, resulting in enhanced oxygen delivery to the electrocatalyst sites.

Influence of Structural Modification of Micro‐Porous Layer and Catalyst Layer on Performance and Water Management of PEM Fuel Cells: Hydrophobicity and Porosity

“…In a neutron radiography study, Spernjak et al. reported that engineered MPLs with hydrophilic additives reduced the amount of liquid water in the cell .…”

“…This observation indicates that the implementation of a more hydrophobic MPL has resulted in an increase in the overall amount of liquid water inside the cell. In a neutron radiography study, Spernjak et al reported that engineered MPLs with hydrophilic additives reduced the amount of liquid water in the cell [14].…”

“…The small pores in MPLs containing a hydrophobic binder cause high capillary pressure, as a result; the liquid water is both withheld in the CL and preferably transported through cracks and larger pores [13]. Numerous studies have investigated the effects of microstructure properties, especially the wettability [14][15][16][17][18][19][20] and porosity of MPLs [21][22][23] on water balance and performance of PEMFC. Theoretical models have predicted that the introduction of adjusted macro-pores in the catalyst layer leads to better performance.…”

Designing Tailored Gas Diffusion Layers with Pore Size Gradients via Electrospinning for Polymer Electrolyte Membrane Fuel Cells

“…Commercial GDL materials are highly porous and have a dual-component design composed of a hydrophobic carbon fiber substrate and a thin microporous layer (positioned next to the catalyst layer) made of dispersed carbon particles within a polymeric binding agent. , The microporous layer (MPL) (pore size ranges from 0.1 to 0.5 μm) provides a high capillary pressure barrier to facilitate membrane hydration, while the hydrophobic carbon fiber substrate (pore size ranges from 10 to 30 μm) provides pathways for excess water egress from the cell. In efforts to manage the transport of water within the PEM fuel cell, both the design of the fibrous substrate and the MPL have received significant attention in recent years. − Pore structure and wettability of the MPL have both been tailored to improve water management at various operating conditions. ,− For instance, Shrestha et al applied a custom hydrophilic MPL coating onto a commercial hydrophobic GDL for fuel cell operation without anode humidification. The hydrophilic MPL coating was found to be effective at retaining liquid water at the catalyst layer (CL)/MPL interface and led to improved membrane hydration and higher cell voltages.…”

Managing the Pore Morphologies of Microporous Layers for Polymer Electrolyte Fuel Cells with a Solvent-Free Coating Technique

“…Chun et al fabricated MPLs with a higher electrochemical performance by adding ammonium salt as a pore former . Other effective additives include lithium carbonate, polymeric pore former, thermal expandable graphite (GP), multiwall carbon nanotubes, − and carbon nanofibers . Manahan et al reported − that laser-perforated MPLs promote PEFC performance.…”